Selenium content of food consumed by Canadians

Emerging evidence on selenoneine and its public health relevance in coastal populations: a review and case study of dietary Se among Inuit populations in the Canadian Arctic

Selenium is an essential mineral yet both deficiency and excess are associated with adverse health effects. Dietary intake of Se in humans varies greatly between populations due to food availability, dietary preferences, and local geological and ecosystem processes impacting Se accumulation into agricultural products and animal populations. We argue there is a need to evaluate and reconsider the relevance of public health recommendations on Se given recent evidence, including the metabolic pathways and health implications of Se. This argument is particularly pertinent for Inuit populations in Northern Canada, who often exceed dietary tolerable upper intake levels and exhibit very high whole blood Se concentrations due to their dependence on local country foods high in the newly discovered Se compound, selenoneine. Since selenoneine appears to have lower toxicity compared to other Se species and does not contribute to the circulating pools of Se for selenoprotein synthesis, we argue that total dietary Se or total Se in plasma or whole blood are poor indicators of Se adequacy for human health in these populations. Overall, this review provides an overview of the current evidence of Se speciation, deficiency, adequacy, and excess and implications for human health and dietary recommendations, with particular reference to Inuit populations in the Canadian Arctic and other coastal populations consuming marine foods.

A review of micronutrients in sepsis: the role of thiamine, l-carnitine, vitamin C, selenium and vitamin D

Sepsis is defined as the dysregulated host response to an infection resulting in life-threatening organ dysfunction. The metabolic demand from inefficiencies in anaerobic metabolism, mitochondrial and cellular dysfunction, increased cellular turnover, and free-radical damage result in the increased focus of micronutrients in sepsis as they play a pivotal role in these processes. In the present review, we will evaluate the potential role of micronutrients in sepsis, specifically, thiamine, l-carnitine, vitamin C, Se and vitamin D. Each micronutrient will be reviewed in a similar fashion, discussing its major role in normal physiology, suspected role in sepsis, use as a biomarker, discussion of the major basic science and human studies, and conclusion statement. Based on the current available data, we conclude that thiamine may be considered in all septic patients at risk for thiamine deficiency and l-carnitine and vitamin C to those in septic shock. Clinical trials are currently underway which may provide greater insight into the role of micronutrients in sepsis and validate standard utilisation.

Whole blood selenium levels in healthy adults from the west of Algeria

The purpose of this study was to assess whole blood selenium levels of 300 healthy adults living in four selected areas of the west of Algeria. Selenium was measured using differential pulse cathodic stripping voltammetry with a detection limit of 29.20 μg/L. The mean of whole blood selenium concentrations was 85.65 ± 21.60 μg/L ranging between 30.90 and 144.04 μg/L. This concentration did not vary significantly (P > 0.05) in relation to the gender of the subject, with concentrations of 87.75 ± 21.30 μg/L in men and 83.95 ± 21.60 μg/L in women group. Individuals older than 60 years had a whole blood selenium concentration significantly lower than the rest of the population. However, the measured selenium concentrations in the residential areas were not statistically different (P > 0.05). A total of 32 (10.70%) individuals exhibited whole blood selenium level below 60 μg/L. These results are similar to those of some European countries but are much lower than data observed in USA or seleniferous regions.

Selenium in reproductive health

Selenium is an essential trace element of importance to human biology and health. Increasing evidence suggests that this mineral plays an important role in normal growth and reproduction in animals and humans, and selenium supplementation is now recommended as part of public health policy in geographical areas with severe selenium deficiency in soil. This review addresses the biological functions of selenium followed by a detailed review of associations between selenium status and reproductive health. In many countries, selenium dietary intake falls below the recommended nutrient intakes and is inadequate to support maximal expression of the selenoenzymes. Numerous reports implicate selenium deficiency in several reproductive and obstetric complications including male and female infertility, miscarriage, preeclampsia, fetal growth restriction, preterm labor, gestational diabetes, and obstetric cholestasis. Currently, there is inadequate information from the available small intervention studies to inform public health strategies. Larger intervention trials are required to reinforce or refute a beneficial role of selenium supplementation in disorders of reproductive health.

Selenium and preeclampsia: A global perspective

Preeclampsia is a complex multisystem disorder of pregnancy where oxidative stress plays an important aetiological role. The role of selenium in the synthesis of endogenous antioxidants is well documented, and a significant reduction in selenium has been reported in preeclamptic women. The objective of this study was to map global selenium status and preeclampsia incidence. This study identified peer reviewed journal articles reporting national preeclampsia incidence (%) and matched these with reported values of selenium intake and plasma/serum selenium concentrations (μg/L). Matched data were obtained for 45 regions, reporting 6456,570 births, spanning Europe, Asia, Australasia, Africa, North and South America. Increasing plasma selenium concentration was found to be correlated with a reduction in preeclampsia incidence (Pearson's r=-0.604, P<0.0001). Countries with a reported serum/plasma selenium level of ⩾95μg/L were considered selenium sufficient and a significant reduction in preeclampsia incidence for countries above this value (P=0.0007) was noted. Significant reductions in preeclampsia incidence were found to coincide with increases in plasma/serum selenium concentration in the New Zealand (P=0.0003) and Finland (0.0028) populations following Government intervention. This study supports the hypothesis that selenium supplementation may be beneficial in reducing oxidative stress in women at risk of preeclampsia.

The role of selenium in chronic disease

Selenium functions as a part of proteins known as selenoproteins. Through these selenoproteins, selenium functions as a defensive mechanism for oxidative stress, for the regulation of thyroid hormone activity, and for the redox status of vitamin C and other molecules. In several of its roles, selenium functions as a dietary antioxidant and thus has been studied for its possible role in chronic diseases. This article reviews recent studies regarding selenium status or supplementation in hypertension, cardiovascular disease, cancer, and diabetes mellitus. A few studies regarding aging and mortality are also included. What can be ascertained from this current review is that the maintenance of adequate selenium nutriture and, at minimum, the prevention of a deficiency in selenium would be advisable for all individuals. In addition, the indiscriminant use of selenium supplements should be approached with caution until further randomized, controlled trials monitor the effects of such supplementation, especially on a long-term basis.

Selenium and aflatoxin levels in raw Brazil nuts from the Amazon basin

Whereas selenium (Se) is an important antioxidant in human metabolism to prevent cancer, aflatoxins are highly carcinogenic. Brazil nuts from Eastern and Western Amazon regions were evaluated to find any relationship between Se and aflatoxins levels. A total of 80 (in-shell and shelled) nuts samples were collected directly from different forest sites and analyzed for Se by atomic emission spectrometry and aflatoxins by liquid chromatography tandem mass spectrometry. The limit of quantitation (LOQ) for Se was 2.0 mg/kg, and LOQ for total aflatoxins was 0.390 microg/kg. Nut Se levels from the Eastern region were higher than the Western, in addition to the aflatoxins. The moisture content (mc) and water activity (aw) of the raw nuts from the two regions did not present a significant difference, for either in-shell or shelled. The mc was 24.5% (minimum of 20.1% and maximum of 30.4%) and 22.1% (minimum of 14.6% and maximum of 28.9%) and a w of 0.85 for both regions. Further studies need to be carried out to discover the role of Se on fungi growth stress and aflatoxin production mechanisms.

The Relevance of Selenium to Immunity, Cancer, and Infectious/Inflammatory Diseases

Selenium is an essential trace element involved in several key metabolic activities via selenoproteins, enzymes that are essential to protect against oxidative damage and to regulate immune function. Selenium also may have other health benefits unrelated to its enzymatic functions. It may provide important health benefits to people whose oxidative stress loads are high, such as those with inflammatory or infectious diseases like rheumatoid arthritis or human immunodeficiency virus/acquired immunodeficiency syndrome, or who are at high risk for cancers, particularly prostate cancer. Some studies have generated compelling evidence that selenium is beneficial, either alone or in conjunction with other micronutrients. Additional data from large clinical trials that provide the highest level of evidence will be key to determining the benefits accrued at various selenium intake levels. When the strength of the evidence becomes sufficient, clinical health professionals will need to use dietary and clinical assessment methods to ensure that people at increased risk for cancer or inflammatory and infectious diseases can be appropriately advised about selenium intake.

Dietary intake of arsenic, mercury and selenium by children from a German North Sea island using duplicate portion sampling

The dietary intake of arsenic, selenium and mercury was studied for children living on the North Sea island Amrum, Germany. Altogether, 98 duplicate portions were collected from 14 children (age 1.5-5.5 years) in April and May 1995 over a sampling period of 7 days, respectively. The element concentrations in duplicate samples were measured by atomic absorption spectrometry. The weekly As and Hg intake (median and range) was 2.31 and 0.89-6.75 microg/(kg(bw) x week) for As and 0.13 and 0.060-0.62 microg/(kg(bw) x week) for Hg. Compared with the provisional tolerable weekly intake (PTWI) for As and Hg as proposed by the WHO, German children from coastal areas reveal no health risks due to As and Hg dietary intake. The daily Se intake (median and range) was 19 and 6-160 microg/day. The appropriate Se intake of 10-40 microg/day, as recommended by the Austrian, German, and Swiss Nutrition Councils for 1-4 years-old children, was not reached in 8 out of 49 cases (16.3%), whereas the recommended Se intake, fixed at 15-45 microg/day for the 4-7 years-old children, was not reached in 15 out of 48 cases (31.3%).

A comparison of methods of assessment of dietary selenium intakes in Otago, New Zealand

The aims of the present study were (1) to compare three methods of assessment of dietary Se intake, i.e. chemical analysis of duplicate diets, diet records and a food-frequency questionnaire (FFQ) designed specifically for Se, and (2) to determine dietary Se intakes of residents of Otago, New Zealand. The FFQ was completed by 110 free-living adults. Diet records (3 d) and duplicate diet collections were carried out by forty-three of these subjects chosen on the basis of low blood Se concentration, and during a period when consumption of the high-Se foods fish, kidney, liver and Brazil nuts was discouraged. Mean Se intakes were similar for duplicate diet analysis (29 (SD 13) micrograms/d) and diet record assessments (28 (SD 15) micrograms/d). Estimates of intakes from the FFQ for the subgroup of forty-three subjects were higher (51 (SD 26) micrograms/d) than those from duplicate diets and diet records. Values from duplicate diet analysis and diet record assessments were strongly correlated (r 0.7, P = 0.0001), but difference plots indicated a lack of agreement between the two methods. Thus, diet record assessment was not adequate for predicting dietary Se intakes of individuals. Significant correlations were found for relationships between Se intake from duplicate diets (microgram/kg body weight per d) and plasma Se, Se intake from diet records (microgram/d and microgram/kg body weight per d) and plasma Se; and Se intake from the FFQ and whole-blood Se. Se intakes from duplicate diets and diet records were similar to those reported previously for New Zealanders, but lower than the recommended intakes in the USA (National Research Council, 1989), Australia (Truswell et al. 1990) and the UK (Department of Health, 1991) and the World Health Organization/Food and Agriculture Organization/International Atomic Energy Agency (1996) normative requirement.

Selenium

The 4 natural oxidation states of selenium are elemental selenium (0), selenide (-2), selenite (+4), and selenate (+6). Inorganic selenate and selenite predominate in water whereas organic selenium compounds (selenomethionine, selenocysteine) are the major selenium species in cereal and in vegetables. The principal applications of selenium include the manufacture of ceramics, glass, photoelectric cells, pigments, rectifiers, semiconductors, and steel as well as use in photography, pharmaceutical production, and rubber vulcanizing. High concentrations of selenium in surface and in ground water usually occur in farm areas where irrigation water drains from soils with high selenium content (Kesterson Reservoir, California) or in lakes receiving condenser cooling water from coal-fired electric power plants (Belews Lake, North Carolina). For the general population, the primary pathway of exposure to selenium is food, followed by water and air. Both selenite and selenate possess substantial bioavailability. However, plants preferentially absorb selenates and convert them to organic compounds. Aquatic organisms (e.g., bivalves) can accumulate and magnify selenium in the food chain. Selenium is an essential component of glutathione peroxidase, which is an important enzyme for processes that protect lipids in polyunsaturated membranes from oxidative degradation. Inadequate concentrations of selenium in the Chinese diet account, at least in part, for the illness called Keshan disease. Selenium deficiency occurs in the geographic areas where Balkan nephropathy appears, but there is no direct evidence that selenium deficiency contributes to the development of this chronic, progressive kidney disease. Several lines of scientific inquiry suggest that an increased risk of cancer occurs as a result of low concentrations of selenium in the diet; however, insufficient evidence exists at the present time to recommend the use of selenium supplements for the prevention of cancer. The toxicity of most forms of selenium is low and the toxicity depends on the chemical form of selenium. The acute ingestion of selenious acid is almost invariably fatal, preceded by stupor, hypotension, and respiratory depression. Chronic selenium poisoning has been reported in China where changes in the hair and nails resulted from excessive environmental exposures to selenium. Garlic odor on the breath is an indication of excessive selenium exposure as a result of the expiration of dimethyl selenide. The US National Toxicology Program lists selenium sulfide as an animal carcinogen, but there is no evidence that other selenium compounds are carcinogens.

Evaluation of selenium exposure in copper refinery workers

Concentrations of selenium in plasma and urine and activity of glutathione peroxidase in erythrocytes were determined in workers exposed to selenium and in a control group. Plasma selenium concentrations were significantly lower in exposed workers compared to the controls. Erythrocyte glutathione peroxidase activity in selenium workers was significantly higher than in the control subjects. Urine selenium concentrations were not statistically different between the two groups. There was a significant positive correlation between plasma selenium concentrations and urine selenium concentrations in workers exposed to selenium. A weak significant positive correlation was found between plasma selenium concentrations and erythrocyte glutathione peroxidase activity in exposed workers. Our results suggest that the lower plasma selenium concentrations in selenium workers may be attributed to an increase of urinary selenium excretion.

Selenium content of chicken meat in Croatia

The selenium content in dark muscle and liver was determined in chicken meat. All samples had been collected from three large meat producing companies in Croatia. The samples were wet digested with a mixture of nitric and perchloric acids. The selenium content was analyzed by hydride generation atomic absorption spectrometry with the recovery from 97.8 to 98.2%. The correlation coefficient of 0.976 was determined after comparison with results of the fluorimetric method. Mean +/- standard deviation of the selenium concentration (ng Se/g dry matter) was 1330 +/- 20, 2000 +/- 30 and 2090 +/- 30 in liver, and 560 +/- 50, 520 +/- 70 and 740 +/- 50 in dark muscle.

Daily dietary intake of copper, zinc and selenium by different population groups in Burundi, Africa

Daily dietary intake of copper, zinc and selenium for different population groups in Burundi, Africa, has been determined, using different sampling strategies, by atomic absorption spectrometry. Recommended daily intakes (RDA, National Academy, USA) are met for copper and zinc. For selenium, especially the rural population risk a deficiency as observed with a daily intake of 17 micrograms. The importance of different types of food in daily intake is discussed. Legumes proved to be an important source of copper, while for selenium fish contributes in a large part in dietary intake. Calculated total daily intakes are compared with intakes recently published for other countries.

Determination of selenium in duplicate diets of residents of Pinhel, Portugal, by neutron activation

A rapid cyclic instrumental neutron activation analysis (CINAA) method has been used to determine the selenium content of 27 duplicate diet samples from each of the 27 districts surrounding Pinhel, Portugal. The accuracy and precision of the CINAA method have been evaluated by analyzing certified reference materials and observed to be within +/- 5-10% for samples containing at least 40 ppb of selenium. The detection limit has been found to vary between 26-42 ppb selenium depending on the sample composition. The average daily dietary intake has been calculated as 37 micrograms of selenium per day.

Selenium in serum as a possible parameter for assessment of breast disease

The level of selenium in blood serum was determined in 33 patients with breast cancer, 13 women with verified mastopathy, and 43 healthy subjects from the Zagreb area. In the second and third quartiles the values of selenium obtained from sick subjects (41-58 micrograms/L) and healthy subjects (73-89 micrograms/L) differed significantly (P less than 0.001). In the group of subjects with mastopathy, serum selenium in the same way ranged from 67-76 micrograms/L and did not differ significantly from the group of healthy women, but differed significantly from the patients with breast cancer (P less than 0.001). Such a result leads to the conclusion that determination of selenium in the blood could be used as a non-invasive diagnostic parameter in clinical assessment of malignant breast disease.

The renal excretion of selenium

The excretion of selenium in urine was determined in West German healthy volunteers. Women excrete 17.7 +/- 4.2 micrograms Se/d and men 19.0 +/- 9.0 micrograms Se/d. The daily selenium excretion per gram creatinine is 13.5 +/- 3.8 micrograms Se/g crea for women and 9.8 +/- 3.3 micrograms Se/g crea for men. The clearance of selenium from the plasma is calculated with 0.18 mL/min. The selenium excretion per day is positively correlated with the 24 h excretion of urea and creatinine. The correlation of the selenium excretion with the urea excretion is most probably owing to the fact that the selenium intake of West Germans is linked primarily to foods with high protein contents. That the selenium excretion is directly correlated with the creatinine excretion is an indicator that the muscle, which accounts for nearly 50% of the whole body selenium in West German adults, influences the selenium excretion in urine. The positive correlation of the selenium excretion with the potassium excretion also indicates that the muscle mass contributes significantly to the selenium excretion in urine. Another indicator that the selenium excretion is influenced by the muscle is that after intensive muscular activity (running), selenium excretion is enhanced. The 24 h selenium excretion is dependent on the glomerular filtration rate of the kidney characterized by the creatinine clearance. This result is important, because if the selenium excretion is used as parameter for the selenium status of humans, the kidney function should be known. This is a limitation for the use of the urinary selenium excretion as parameter for the selenium status. This is especially important for patients whose glomerular filtration rate is low. The 24 h selenium excretion is further influenced by the 24 h urine volume. Selenium losses via urine may be concomitant with protein losses in urine.

The daily dietary selenium intake of West German adults

The selenium content of food consumed in the Federal Republic of Germany (FRG) was determined for the estimation of the dietary selenium intake of West German adults. The daily dietary selenium intake of men is 47 micrograms (micrograms) and that of women 38 micrograms, corresponding to 0.67 microgram/kg body weight per day for both men and women. Animal protein is the main source of dietary selenium, accounting for 65.5% of the total selenium intake. Pork contributes 25.1% to the total Se intake, reflecting the current consumption and the selenium supplementation of feedstock rather than the availability of selenium from natural dietary sources. The selenium intake of adults in West Germany is only slightly higher than in New Zealand, Finland, and Italy, nearly equal to that in Belgium and France, and distinctly lower than in Great Britain, the USA, Canada, and Japan.

Platelet glutathione peroxidase activity is impaired in patients with coronary heart disease

Platelet glutathione peroxidase (GSH-Px) activity was measured in 25 healthy individuals and in 25 patients affected with well-documented coronary artery stenosis. In parallel, malondialdehyde (MDA) production was assayed on platelets following stimulation with sodium arachidonate. Mean platelet GSH-Px activity was significantly reduced and mean platelet MDA production was significantly increased in the patient group. The difference observed in the GSH-Px activity might be a consequence of different nutritional habits, suggesting an impaired intake of selenium, the inorganic moiety of GSH-Px. As low GSH-Px activities in human platelets may be associated with increased MDA and thromboxane production, we hypothesize that a low enzyme activity may be a risk factor for the development of coronary artery disease.

Selenium intake of infants and young children, healthy children and dietetically treated patients with phenylketonuria

In 20 healthy infants and children, 5-20 months old, the Se intake was estimated by analysing food samples by instrumental neutron activation analysis. The intake was calculated by weighing the portions offered and actually consumed. The median Se content of the food amounted to 27 ng/g wet weight (gww) and median daily Se intake to 33.5 micrograms. The Se intake was not equally distributed over the day. About 50% of the daily Se intake was derived from the supper. The main Se sources (41%) for young children were cereal paps. Commercially available meals (30 ng/g) contained less Se than home-made ones (50 ng/g). In nine dietetically treated patients with phenylketonuria the median Se intake amounted only to 6.9 micrograms/day corresponding to a mean Se content of the diet of 7.9 ng/g. The main Se source in the diet was vegetables (36.3%) and 20% derived from their protein supplements. The Se intake of young children, healthy or dietetically treated, cannot be calculated accurately from tables but must be estimated by measuring the Se content of the local food because cereals and vegetables--the main Se sources--exhibit great regional variations.

Dietary selenium intake in Belgium

The estimation of the dietary selenium intake in Belgium has been carried out. Average concentration levels in different food classes, as determined by hydride generation atomic absorption spectrometry are used combined with dietary consumption records or production, importation and exportation statistics. Analysis of duplicate meals has been used as an alternative evaluation method. Dietary intake of selenium in Belgium is discussed and compared with intakes published for other different countries.

Chromium, selenium, and other trace element intakes of a selected sample of Canadian premenopausal women

Daily Cr, Se, Ag, Cs, Rb, Sb, and Sc intakes of 84 Canadian women aged 30.3±6.1 yr (mean±SD) living in a University community and consuming self-selected diets were determined by analyses of 1-d food composites collected by the subjects. Aliquots of the homogenized food composites were freeze-dried and then analyzed by instrumental neutron activation procedures following irradiation for 72h. In all cases, trace element concentrations in the food composites were non-Gaussian. Median daily intakes were: Cr, 47 μg; Se, 74 μg; Ag, 7.1 μg; Cs, 4.4 μg; Rb, 1.5 mg; Sb 2.0 μg; and Sc, 0.38 μg. Sixty percent and 24% of the subjects received daily Cr and Se intakes, respectively, below the US Food and Nutrition Board safe and adequate range. High Cr density diets were associated with a significantly higher consumption of cheese and dry legumes and nuts (p<0.05). In the high Se density diets, intakes of grain products and breakfast cereals were significantly higher (p<0.05), and intakes of potatoes, table fats, total fat, saturated fat, and oleic acid were significantly lower (p<0.05) compared to the low Se density diets. The low daily Cr intakes evident in this study may be cause for concern in view of the increasing evidence that women may be at greater risk for deficiency of Cr than men because of Cr depletion during pregnancy.

Pesticides and other chemical residues in Dutch total diet samples (June 1976-July 1978)

Over a period of 2 yr 126 different food items of a market basket of 16-18-yr old males were purchased every 2 months. The foodstuffs were prepared as for eating, and were combined in 12 commodity groups. Twelves samples of each food group were homogenized and analysed for 78 different chemicals, including pesticides, PCBs, bromine, heavy metals, arsenic and selenium. Thirty-four of these chemicals were detected in the various samples and the means and ranges of residue concentrations found in each food group are reported. Most chemicals were found in concentrations below the Dutch residue tolerance limits, the two exceptions were omethoate and carbendazim. Using the concentrations found in the total diet samples the daily intakes of the various chemicals were calculated. The daily intake figures were evaluated with the aid of the Acceptable Daily Intakes (ADI) recommended by FAO/WHO. For practically all chemicals examined the mean and the maximum intakes were well below the ADI.

Exposure of man to environmental selenium - an exposure commitment assessment

Selenium is an element which occurs naturally in varying concentrations in soil and is released from industrial sources, particularly from fossil fuel combustion. Harmful effects in animals and man may result from both deficient or excessive amounts of intake. Representative values of selenium concentrations in the background environment and in man are selected from available data and a pathway analysis is performed utilizing the exposure commitment method. Dietary intake of selenium is of the order of 70 micrograms d-1. With fractional absorption of 80% and retention in the body of 90% for an effective retention time of 140 days, the estimated mean body content of selenium is 7 mg. The contribution to the body burden from inhalation intake is much less significant. The exposure evaluation is performed for total selenium in the environment and in man. The parameters may be adjusted for specific selenium compounds, if data are available, and for more particular environmental and exposure conditions as required.

Selenium in environmental and drinking waters of Belgium

The tetravalent and hexavalent selenium content of water samples can be determined by conventional energy-dispersive X-ray fluorescence after different preconcentration steps. Selenium values of nearly three-hundred different environmental and drinking water samples in Belgium are reported. The results are quite low, ranging from the detection limits up to 1 microgram 1-1. The concentration levels are compared to literature data and the speciation is discussed. The contribution of drinking water to the daily intake of selenium in Belgium ranges from less than 0.2 to 5%.

Trace element intakes of women

1. Energy, protein, zinc, copper, manganese, selenium and dietary fibre intakes of 100 pre-menopausal women (mean age 30.0 +/- 6.1 years) from a university community, and consuming self-selected diets, were calculated using 3 d dietary records and food composition values. Subjects also collected a 24 h food composite during the 3 d record period for analysis of Zn, Cu and Mn by atomic absorption spectrophotometry. Daily analysed intakes were compared with those calculated from the corresponding record day. 2. Mean daily calculated intakes of energy, protein, Zn, Cu, Mn, Se and dietary fibre were 7.54 +/- 1.61 MJ, 74 +/- 18 g protein, 10.1 +/- 3.3 mg Zn, 1.9 +/- 0.6 mg Cu, 3.1 +/- 1.5 mg Mn, 131 +/- 53 micrograms Se, 19.4 +/- 6.6 g dietary fibre. 3. Major food sources for each of the trace elements were (%): Zn meat + substitutes 43, dairy products 23.7; Cu breads and cereals 22, vegetables 21; Mn breads and cereals 47, fruits 12, Se meat + substitutes 38, breads and cereals 30. 4. Highly significant correlations (P = 0.001) were noted for analysed intakes of Zn, Cu and Mn and those calculated from the corresponding record day. Mean calculated intakes were higher (%): Zn 138, Cu 142, Mn 121, than corresponding mean analysed intakes (P = 0.01). However, the mean nutrient densities (mg/MJ) were comparable: Zn analysed 1.2, calculated 1.4; Cu analysed 0.2, calculated 0.2; Mn analysed 0.4, calculated 0.4. 5. All subjects met the Canadian Dietary Standard (CDS) recommended level for Cu but 48% received less than the CDS for Zn, 6% obtaining less than two-thirds of this recommended level. Daily Mn and Se intakes were similar to recent values for North American diets.

Selenium supplementation in total parenteral nutrition

Four adult patients with very low plasma selenium (Se) levels ( less than or equal to 1.5 microgram/100 ml) were given Se supplements while receiving total parenteral nutrition. A comparison was made using the compounds selenomethionine and sodium selenite given either intravenously or by mouth. Urinary excretion and Se plasma responses differed, and indicated that selenomethionine retention was greater. However, the incorporation of Se into the erythrocyte and its enzyme glutathione peroxidase was unpredictable and delayed and was not a good indicator of supplement response. No deleterious effects of supplements were observed. Se supplements are indicated especially in patients with a high risk of developing low Se levels and are best monitored by plasma Se levels.

Selenium requirements in patients with inborn errors of amino acid metabolism and selenium deficiency

The diets of 5 patients with phenylketonuria of maple-syrup-urine disease were supplemented with yeast which was rich in selenium. For 120 days the patients received 45 micrograms Se/day to increase the Se content of their diets to 10--12 ng Se/Kjoule. Before supplementation the selenium content of serum (5--15 ng/ml) and whole blood (10--27 ng/ml), and the activity of the erythrocyte glutathione peroxidase (0.19--2.69 U37/g Hb), amounted to only 10--20% of normal. The serum selenium content reached normal values within 4 weeks of supplementation, followed by normalisation of the selenium content of whole blood within 4--8 weeks. Restoration of the activity of erythrocyte glutathione peroxidase took 9 to 15 weeks--the red cell life span. There was a significant positive correlation between the selenium content of the erythrocytes and the activity of erythrocyte glutathione peroxidase.

Neonatal erythrocyte glutathione peroxidase deficiency as a consequence of selenium imbalance during pregnancy

The red blood cell (RBC) glutathione peroxidase (GSH-Px) activity and routine haematological parameters were measured in 38 healthy north Italian full-term pregnant women and in their newborn infants. In 31 pairs the serum selenium concentration was also measured. Data were compared with those of 20 normal adult controls (10 males and 10 females). Newborn infants exhibited significantly lower RBC GSH-Px activity and serum selenium concentrations than adult controls. Pregnant women had serum selenium values intermediate between those of adult female controls and their newborn infants. In both the pregnant women and newborns the RBC GSH-Px activity correlated with the level of selenium in serum which suggests that the neonatal RBC GSH-Px deficiency may be partially due to insufficient availability of selenium during pregancy. Factors other than selenium concentration, e.g. hormonal and genetic, might also affect the RBC GSH-Px activity as suggested by sex differences and mother/child concordances in enzyme activity found in our cases.

Selenium content of human milk, cow's mild and cow's milk infant formulas

The selenium content of human milk, cow's milk and cow's milk infant formula were estimated by instrumental neutron activation analysis. The highest values were found in 3 samples of human colostrum (524--865 x 10(-9) g/g dry weight). There was a significant decrease with increasing time post partum. Mature human milk exhibited a selenium content of 230 +/- 79 x 10(-9) g/g dry weight. The selenium content of 45 samples of cow's milk from the north-western area of Germany was 200 +/- 39 x 10(-9) g/g dry weight. While there was no significant difference between the values of mature human milk and of cow's milk, cow's milk infant formula exhibited significantly (P less than 0.01) lower values than human milk. The average selenium content of 107 samples of 10 different commercially available fluid and powdered cow's milk infant formulas (range: 18--171 x 10(-9) g/g dry weight) amounted to about only one third of that in mature human milk.

Quantitative selenium metabolism in normal New Zealand women

1. Quantitative selenium metabolism has been studied in normal young New Zealand women by measuring total Se intake and urinary and faecal Se output, and by using values for absorption, excretion and turnover of 75Se determined after administration of[75Se]selenomethionine or [75Se]selenite. 2. In a period of 14 d when a normal ad lib. diet was being consumed, mean dietary Se for four women was 24.2 microgram/d, mean urinary Se was 13.1 microgram/d and mean faecal Se was 10.8 microgram/d; mean Se balance during this time was + 0.3 microgram/d. 3. Intestinal absorption of food Se was 0.76--0.83 of intake (mean 0.79). 4. Whole-body Se was calculated in three different ways; (a) using the specific activity of urinary Se and retained whole-body 75Se; (b) using plasma Se and the occupancy of 75Se in whole-body and plasma; (c) using absorbed food Se and the occupancy of absorbed 75Se in whole-body. 5. Whole-body Se calculated from measurements obtained following the administration of [75Se]selenomethionine was 4.7--10.0 mg (mean 6.9) using method (a), 4.1--7.2 mg (mean 5.2) using method (b) and 4.3--8.9 mg (mean 6.2) using method (c). 6. Whole-body Se calculated from results obtained after giving [75Se]selenite was 2.7--3.4 mg (mean 2.9) using method (a), 2.3--5.0 mg (mean 3.5) using method (b) and 2.1--3.0 mg (mean 2.6) using method (c). 7. The results of this study indicate that the minimum dietary requirement of Se for the maintenance of normal human health is probably not more than 20 microgram/d.

In vivo and in vitro variations of human erythrocyte glutathione peroxidase activity as result of cells ageing, selenium availability and peroxide activation

Cases showing erythrocyte glutathione peroxidase (GSH-Px) defects have been previously described. Our experiments demonstrate that a number of non genetic factors may influence the GSH-Px activity in human erythrocytes. Selenium administration in vivo was followed in four subjects by elevation in erythrocyte GSH-Px activity ranging from 30% to 1400%. Selenium operates mainly in the bone marrow erythroblasts by facilitating the synthesis of active GSH-Px molecules; experiments in vivo demonstrate that, in the youngest erythrocytes, selenium can raise the enzyme activity, but by a different mechanism. The reticulocyte GSH-Px activity appears to depend on selenium availability and may vary over a wide range. In some normal and iron deficient subjects the GSH-Px activity in the youngest erythrocyte fraction was equal or lower than that previously found in whole erythrocytes of patients affected by haemolytic anaemia. During erythrocyte life, GSH-Px activity may either diminish or increase, and these variations are inversely related to the initial GSH-Px activity in youngest cells. In vitro experiments with the addition of acetyl-phynyl-hydrazine strongly suggest that elevation of GSH-Px activity may be due to allosteric enzyme activation by activated oxygen.